Collapsible gantry



Feb. 27, 1940. E. G. MALPAS 2,191,697

SPRING FOR PISTON RINGS Filed May 23, 1938 Patented Feb. 27, 1940 UNITED STATES COLLAPSIBLE GANTRY Benjamin Jacoby and John M. Quigley, Marion,

Ohio, assignors to The-Marion Steam Shovel Company, Marion,

Ohio, a corporation of Ohio (Incorporated in 1927) Application October 17, 1936, Serial No. 106,151

24 Claims.

This invention relates to a collapsible gantry for excavating machines or other machines hav- 7 ing booms.

, The ordinary excavating machine has a for- 5 Wardly and upwardly inclined boom which is usually supported at a fixed inclination but which is adjustable to different inclinations according to the demands of the work. This boom is supported from a gantry, sometimes called an 'A-frame, which is mounted on the platform of the machine, usually by means of a cable which is connected with the point of the boom and extends about a sheave on the gantry to a hoisting v drum on the platform, whereby the vertical movement of the boom may be controlled and it may be adjusted to the desired inclination. The

height of this gantry is limited by the fact that the machine in traveling from one point to another must pass under overhead structures, wires 20 and thelike which would obstruct the movement of a high gantry. The ordinary gantry provides a satisfactory support for the boom in its higher elevations but when the boom is lowered to a position in which its point is near the level of the top of the gantry the cable comes so nearly parallel to the boom that it does not provide a satisfactory support and it places the boom under relatively great compression stresses. It is therefore highly desirable, particularly in the case of booms of relatively great length, toprovide a gantry of such height that the cable will extend at such an angle to the boom, in all positions of the latter, as to provide a satisfactory support therefor and to avoid undue stresses.

It is the primary object of my invention to provide a gantry of relatively great height which willbe collapsible to permit it to pass under any overhead structure under which the usual gantry could pass.

an A further object of the invention is to provide a collapsible gantry of such a character that it can be easily and quickly collapsed to permit the machine to pass under an overhead structure and then quickly and easily restored to its extended position.

A further object of the invention is to provide a collapsible gantry of such a character that it will support the boom while in its collapsed condition, thereby permitting the machine and the boom, as a whole, to be moved under the overhead structure.

- Afurther object of the invention is to provide a collapsible gantry the several parts of which M "will be so constructed and arranged that no part (if the structure can contact with the boom in any position to which the gantry may be moved. A further object of the invention is to provide a gantry of such construction that it may be installed on existing machines by the addition of parts to the ordinary gantry, with little or no change in that'gantry or other parts of the machine.

A further object of the invention is to provide such a collapsible gantry which will be simple in its construction, of a strongrigid character and which may be produced at a relatively low cost.

Other objects-"cf the invention may appear as the device is described in detail.

In the accompanying drawings Fig. 1 is a side elevation of the forward portion of a dragline excavator,'partly broken away, showing a collapsiblegantry' installed thereon; Fig. 2 is aside elevation of a portion of the machine, partly broken.

chines of. various kinds, Without departing from the spirit of the invention.

The machine here shown is a dragline of ordinary construction and comprises a base ID carried by suitable traction devices II and having mounted thereon a rotatable platform [2 on which the various parts of the excavating mechanism are mounted, the machinery being enclosed in a housing I3. A boom [4 is mounted at its foot upon the platform 12 and an excavating scoop I5 is supportedfrom the point of the boom by a cable It which extends about a sheave I! on the boom and thence rearwardly to the platform ,Where it is wound on a power operated drum, which is not here shown but which is mounted on a shaft 18. The scoop is moved through the material to be excavated, toward the machine, by a drag cable l9 connected with the open end of the-scoop by means of a bridle 20 and wound ,on a power operated drum also mounted on the shaft I8. The two drums are separately operable to first fill the scoop and,

then hoist the same to permit it to be moved-to dumping position by, swinging the boom.

The boom is supported at the desired inclinato maintain the tension of the ring against the cylinder wall at the place where it is cut in providing the parting at 6.

In Fig. 1 I have shown three forms of the spring spreader member or elements. Those at the lower side of Fig. 1 and at the right-hand side are each provided with a plain curved middle section I l. The one at the upper side of Fig. 1, and also as shown in Fig. 3, has such curved section ll provided with outwardly pressed ribs or humps I6, so spaced apart that they will come directly within the ends of the curved slot at 9 where said slot breaks through to the inside of the piston, in this manner providing a positive location of the spring spreader member in its seat. An equivalent is shown in Fig. 4, and also at the left side of Fig. 1, where instead of the ribs or humps l6, tongues l? are struck from the middle section II occupying the same relative position as the ribs I6 and serving the same purpose. Said tongues at their outer ends are formed with outwardly curved detents which snap over the metal of the piston at the opposite ends of the inner end of the slot 9 and retain the spring spreader against accidental disengagement.

While I have shown the expander in connection with an oil ring, it is evident that it may also be used with the regular compression rings which are solid in cross section and do not have any oil carrying grooves therethrough. In such case it is not necessary to out the arc-shaped slots 9 through to the interior of the piston, nor will it be necessary to use the oil passages 3. The invention, therefore, contemplates the use of the expander both for oil rings and for compression rings and with the cutting of are -shaped seats at the bottom of the ring groove for the intermediate or middle sections of the expanders without necessarily cutting through to the interior of the piston.

With the construction described a very practical and useful spring tension spreader for piston rings is provided. The assembly of the spring members with the piston and the piston ring is very simple and easy. As" previously stated, the location within the ring may be Widely varied and also the number which be used with the different sizes of pistons and rings may be varied to obtain the best results.

The invention is defined in the appended claims and is to be considered comprehensive of all forms of structure coming within their scope.

I claim:

1. In combination with a hollow piston having a piston ring groove therein, said piston at a plurality of spaced apart points therearound having arc-shaped slots cut from the bottom of the groove through to the inner side of the piston, a piston ring in said groove, and a spring expander member seated at each of said slots having an arc-shaped intermediate portion received in the slot and bearing at its end portions against the arc-shaped ends of the slots, and said spring member also comprising a spring extension at each end of said arc-shaped intermediate section against which the inner side of the piston ring bears.

2. In combination with a hollow piston having a piston ring groove therein, said piston at spaced apart points therearound and extending inwardly from the bottom of said groove having slots cut through to the interior of the piston, the ends of said slots being substantially of concave form, a parted piston ring in said groove, and spring expander members of thin spring material, each having a middle portion shaped to be received in said slots and bear at its ends against the concave ends of said slots", said intermediate portion at the central part thereof extending into the interior'oi the piston, and said spring members at eachend of the intermediate portion being bent into substantially S-shape and terminating in oppositely extending free extensions bearing against the inner curved side of the piston ring.

. one at each end or" and at the inner sides of said slot.

5. In combination with a piston having a piston ring groove therein, said piston having a p1urality of spaced apart slots cut therethrough from the bottom of the groove to the inner side of the piston, a parted piston ring in said groove, and

spring expander members between the piston and the inner side of said piston ring, one at each of said siots, each of said spring members having an intermediate portion seated at its ends against the piston at the ends of a slot, said intermediate portion at each end thereof having an outwardly extending yielding spring extension bearing against the inner curved side of the piston ring and adapted to be pressed inwardly toward the bottom or" the ring groove when the piston ring is contracted.

6. The combination with a piston having a groove therein and an armshaped seat in said groove communicating with the interior of said piston, of a piston ring expander comprising, a length of spring material formed with a middle section curved substantially in the arc of a circle of substantially the same radius as the arc of said seat and adapted to be inserted therein, said section at its ends being continued in a return bend for a distance less than half the length of said middle section and thereafter being again return-bent to provide two free terminal sections extending oppositely to each other.

'7. The combination with a piston having a groove therein, an arc-shaped seat in said groove communicating with the interior of said piston and a piston ring therein, of a piston ring expander comprising, an arc-shaped intermediate portion to be received in said seat and bearing at its ends against the ends of said seat, and a spring extension at each end of said intermediate section against which the inner side of the piston ring bears.

8. The combination of elements defined in claim 7, combined with means on said expander for enga ing with the ends of said seat to locate said expander in a predeterminedposition and hold it in said position.

ELLIS G. MALPAS.- 

